This application claims the priority of Japanese Patent Application No. 2000-232811 filed on Aug. 1, 2000 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a linear transmission member driving unit for an endoscope, and more particularly to a structure of a driving unit for rotating, by a motor, a linear transmission member for changing an observation distance (including changing depth of field).
2. Description of the Prior Art
FIGS. 4 and 5 show a structure (for example, Japanese Patent Laid-Open No. 2000-111806) of an endoscope, to which a mechanism for making an observation distance (or depth of field) variable is applied, and first with reference to FIG. 5, the description will be made of the endoscope as a whole. The endoscope is constituted by an operating unit 1A, an insertion portion 1B having flexibility and a tip end portion 1C, and the operating unit 1A is provided with a air-supply/water-supply operating button 2A, a suction operating button 2B, a freeze switch 3, an observation distance variable switch 4 and the like. This observation distance variable switch 4 is capable of changing a focal length to a far direction or a near direction.
In this operating unit 1A, a motor 7 is mounted on a chassis 6 by means of a holding member 8, and to this motor 7, a linear transmission member 10 consisting of a multiple coiled spring is mounted through a shaft connector 11. This linear transmission member 10 is inserted in a protective tube 12 for preventing any interference with other members, and this protective tube 12 is attached to the chassis 6 by means of the holding member 13. These linear transmission member 10 and protective tube 12 are arranged from the operating unit 1A to the tip end portion IC through the insertion portion 1B.
At this tip end portion 1C, there are provided an objective optical system 14 and a CCD 15, which is a solid state imaging device, and a movable lens installed in this objective optical system 14 for making the observation distance variable is driven by the linear transmission member 10. More specifically, as shown in FIG. 4, at the tip end portion 1C, there are arranged a front-side lens 17, a movable lens 18, and a prism 19, and below the prism 19, a CCD 20 is optically connected. The holding member 22 of the movable lens 18 has a female threaded portion in its top portion, and there is arranged a rotary driving member 23, whose male threaded portion threadedly engages this female threaded portion, and to this rotary driving member 23, the linear transmission member 10 is coupled.
Further, the rotary driving member 23 is provided with a first stopper 25A having a male threaded portion at its end and a second stopper 25B in such a manner that the inside of a wall portion, in which the inside diameter at a rear end of the holding member 22 becomes smaller, abuts on the first stopper 25A, and the outside abuts on the second stopper 25B.
According to such structure, rotation of the motor 7 is transmitted to the rotary driving member 23 at the tip end portion 1C through the linear transmission member 10, and the rotational motion of this rotary driving member 23 is converted into a straight-line motion by means of a combination of threaded engagement with the holding member 22. Thereby, the movable lens 18 moves back and forth within a range D1 (FIG. 4) to be set by the first stopper 25A and the second stopper 25B, and it becomes possible to change the observation distance to be set by the objective optical system.
In the above-described linear transmission member driving unit, however, the linear transmission member 10 consists of a multiple coiled spring, by means of which the operating unit 1A and the tip end portion 1C are coupled over a comparatively long distance therebetween, and therefore, driving control is not linearly performed, but particularly the response at the driving end (terminal end) is not satisfactory. More specifically, in the driving control of the motor 7, the holding member 22 of the movable lens 18 abuts on the first stopper 25A or the second stopper 25B to reach the driving end, and when a load to be given to the rotating shaft of the motor 7 through the linear transmission member 10 exceeds a predetermined value, the motor 7 is controlled to be stopped.
However, since the rotary driving force to be transmitted from the motor 7 is absorbed by the kink of the linear transmission member 10, no stop control is performed in the control circuit before a fixed amount of load is applied to the motor 7 since the movable lens 18 stops at the driving end. Also, even when the direction of rotation is reversed at the driving end, since the movable lens 18 starts to move after the kink of the linear transmission member 10 is completely returned, a time lag occurs between when the observation distance variable switch 4 is operated, and when actually driven, and as a result, the operability is worsened.
Also, in order to move the movable lens 18, a force to be given to the tip end portion driving member is increased by the kink of the linear transmission member 10, and since a miniaturized driving member is used for the tip end portion of the endoscope which has particularly a fine diameter, the durability of the tip end portion driving member is deteriorated. Similarly, there was a problem that the durability of the linear transmission member 10 itself is also deteriorated due to the kink.
As means for avoiding such a problem, it can be conceived to reinforce the linear transmission member 10, and to increase its diameter so as not to cause any kink phenomenon even for the maximum driving force for improving the transmission ability. Even in this case, however, it is possible to reduce the time lag between during operating and during driving to some extent, but sufficient response cannot be obtained. And yet, this observation distance variable operation is structured so as to be able to change the operating speed stepwise, and since the linear transmission member 10 becomes heavier by increasing the diameter, it becomes difficult to execute high-speed operation.
Also, when the diameter of the linear transmission member 10 is increased, the hardness also becomes higher, and therefore, the transmission characteristic of the linear transmission member 10 is deteriorated because of a change in posture of the insertion portion 1B which can be freely bent, and there is also an inconvenience that there occurs a difference in time required for the observation distance variable operation.
The present invention has been achieved in view of the above-described problems, and an object of the present invention is to provide a linear transmission member driving unit for an endoscope capable of obtaining high operability in the function for making the observation distance variable and the like by improving the response of driving control, and improving durability of the tip end portion driving member and the linear transmission member.
In order to achieve the object, according to the present invention, there is provided a linear transmission member driving unit comprising: a linear transmission member which rotates to drive an object; a motor, to which this linear transmission member is shaft-connected; a guide member for regulating a range of movement of the object driven by the linear transmission member; and a rotation stopper mechanism arranged between the linear transmission member and the motor, for stopping the rotation of the linear transmission member correspondingly to a range of movement of the object regulated by the guide member.
The another invention is characterized in that it is arranged such that rotation of the linear transmission member is transmitted to a lens driving unit, to make a movable lens for performing a predetermined function move back and forth within a predetermined range, and a range of rotation of the linear transmission member set by the rotation stopper mechanism is set to be equal to or more than a range of rotation of linear transmission member required for the lens driving unit to accomplish a predetermined function.
According to the above-described structure, the rotation stopper mechanism is arranged in the vicinity of the motor shaft, and by means of this stopper mechanism, there is secured a little larger range than the range of movement of the movable lens which accomplishes (ensures), for example, the observation distance variable function (scaling function) to stop the rotation of the linear transmission member. As a result, the kink of the linear transmission member is suppressed to a minimum, and the response of the movable lens can be enhanced under the rapid stop control of the motor.
The another invention is characterized in that there is provided a movable shaft coupling mechanism for coupling an end portion of the linear transmission member to a shaft of the motor, and enabling the linear transmission member to move in a motor rotating shaft direction.
According to the above-described structure, since the end portion of the linear transmission member is coupled to the motor shaft by means of the movable shaft coupling mechanism, even if the linear transmission member expands or contracts because of a bending operation or the like of the endoscope insertion portion, that amount corresponding to the expansion and contraction can be absorbed within the coupling mechanism, the load to be applied to the motor rotating shaft can be made substantially constant, and a scaling operation or the like can be performed by a stable rotary driving force.
The another invention is characterized in that the rotation stopper mechanism is constructed of: a rotating member integrally provided on the outer periphery of the shaft connecting member of the movable shaft coupling mechanism and having a protruded portion; and a locking portion for locking a protruded portion of this rotating member, and that the rotating member is arranged in an outer peripheral position of the motor shaft by providing the motor shaft with a notch portion, through which a screw for mounting the shaft connecting member is inserted.
According to the above-described structure, the shaft connecting member is mounted to the motor shaft while a screw is being inserted through the notch portion provided in the rotating member of the rotation stopper mechanism, whereby the stopper mechanism can be arranged at an outer peripheral position of the motor shaft, and a stable stop operation can be obtained. Also, the rotating member can be easily mounted.
The another invention is characterized in that in the rotating member of the rotation stopper mechanism, its protruded portion is formed with a tapped hole, and the rotating member concerned is screwed and fixed to the shaft connecting member through this tapped hole on the protruded portion.
According to the above-described structure, since screwing and fixing are performed through a tapped hole formed in the protruded portion of the rotating member, sufficient strength can be secured for the tightening and fixing, and the range of rotation can be set large through the use of all the portions other than the protruded portion.